Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$99.38	3.595%	$102.9527	$102.95	$102.95	$103.00
Purchase #2	$55.36	3.179%	$57.1199	$57.12	$57.10	$57.10
Purchase #3	$161.37	13.155%	$182.5982	$182.60	$182.60	$182.60
Purchase #4	$9.91	7.599%	$10.6631	$10.66	$10.65	$10.70
Purchase #5	$172.38	7.385%	$185.1103	$185.11	$185.10	$185.10
Purchase #6	$143.48	8.639%	$155.8752	$155.88	$155.90	$155.90
Purchase #7	$116.34	12.832%	$131.2687	$131.27	$131.25	$131.30
7 purchase totals =	$758.22		$825.5881	$825.59	$825.55	$825.70